WO2001002294A1 - Novel mineral compositions for use as hydroxyapatite precursors, use for reinforcing concrete - Google Patents

Abstract

The invention concerns mineral compositions, for use as precursors, with a chemical composition based on the following systems: CaO-P2O5-Na2O-SiO2 and CaO-P2O5-SiO2. The invention also concerns a method for preparing said compositions, their use for preparing hydroxyapatite, in particular in the form of fibres, for example in concrete mixtures.

Description

 NEW MINERAL COMPOSITIONS FOR USE

AS HYDROXYAPATITE PRECURSORS

APPLICATION TO THE REINFORCEMENT OF CONCRETE

The present invention relates to new mineral compositions which can be used for the preparation of hydroxyapatite, in particular in the form of fibers. These compositions can, in particular, be used for reinforcing materials after an in situ generation of fibers by hydration.

Fibers of apatite structure are known for their reinforcing properties of materials, in particular in plastics, biocompatible materials (bones, teeth, etc.).

Calcium hydroxyapatite is the common name given to a family of compounds with similar structures, but do not necessarily have exactly the same chemical composition. Crystallographically, the apatite structure crystallizes in the hexagonal system. For hydroxyapatite Ca ₁₀ (PO ₄ ) ₆ OH ₂ , the elementary mesh, 5 i.e. the basic construction unit of the apatite crystal) contains 10 Ca atoms, 6 PO _{4 units} and 2 units OH. Among the compounds of apatite structure, we can cite, for example:

- compounds with partial substitution for the Ca ²⁺ ion and / or for the PO ₄ ² "groups,

- the lacunar compounds,

- non-stoichiometric compounds of the Ca ₁₀ _ _x (HPO ₄ ) _x (PO ₄ ) ₆ _ _x OH _{2-x type} .

Hydroxyapatite entering many biological systems (water, bones, ...), its crystallization has been widely studied. Thus, K. Ishikawa and ED Eanes (J. Dent. Res., 1993, Vol. 72, n ° 2, 474-480) highlights the influence of pH on the morphology of the crystals obtained: crystals of isotropic morphology develop at pH 7. In general, obtaining fibrous hydroxyapatite is linked to a control of the concentrations of Ca ²⁺ , PO ₄ ³ "and OH- of the reaction medium: this control must define a well-defined supersaturation with respect to the hydroxyapatite solubility product M. Kinoshita et al. (Gypsum and Lime, n ° 219, 1989, 79-87) were thus able to prepare fibrous hydroxyapatite in aqueous medium in Ca ²⁺ diluted media and in the presence of urea.

Thus, usually, this fibrous morphology is obtained in a medium very rich in water allowing control of the concentration conditions. Given the current state of the art, these hydroxyapatite fibers are not obtained in a medium that is not very rich in water.

One consequence of this technical constraint is that it is not possible to create these fibers in situ, in the very environment of the application to be reinforced by the fibers, because the water content is often low. This low water content also considerably increases the concentrations of parasitic impurities.

In the specific case of concrete, organic or mineral fibers are incorporated into the mortar, during the mixing of the hydraulic binder, water and aggregates They provide the final concrete with improved mechanical properties The incorporation of these fibers on an industrial scale different problems The shaping of the mortar requires delicate operations, on the one hand, to avoid breaking the fibers, and, on the other hand, to obtain a paste with correct rheology in order to minimize the amount of water of hydration The possibility of creating fibers m situ, that is to say in the cement composition or the concrete itself would be a solution to these problems of shaping the mortar

To obtain reinforcing properties, it is necessary to control the chemical composition and the nature of the fibers generated. The main difficulty to be resolved is to control, on the one hand, on the one hand, the hardening and setting operations of the concrete, and , on the other hand, the development of fibers, difficult in these environments which are not very rich in water and moreover, concentrated in impurities such as Na ⁺ , K ⁺ , SO ₄ ^2_ , Ca ²⁺ , the silicate anions In addition, this development fibrous must be carried out in a medium at basic pH, characteristic of cement media

An object of the present invention is to provide a hydroxyapatite precursor which can lead to the formation of hydroxyapatite, in particular in the form of fibers, from a small amount of water.

Another object is to propose a hydroxyapatite precursor which can create hydroxyapatite, in particular fibers, inside the application medium itself, so as to avoid the introduction of the fibers during the preparation of the medium. Application

Another object of the present invention is to find a way to avoid adding fibers during the preparation of concrete, in particular by forming fibers in situ

Mineral compositions

For these purposes, the subject of the invention is mineral compositions based on the CaO-P ₂ O ₅ -SιO ₂ system or the CaO-P ₂ θ5-Sιθ2-Na ₂ 0 system which can generate hydroxyapatite fibers by hydration The invention relates, first of all, to a first mineral composition, called type 1, a hydroxyapatite precursor, in particular of fibers, having a chemical composition defined in the following system: CaO-P ₂ O ₅ -SiO ₂ , in the molar proportions such that the ratios (Ca: P: Si) = (1: y: z) satisfy the following conditions (a): 0.5 <y <0.8

0.2 <z <0.6.

This is the overall chemical composition, which does not mean that the precursor understands or only understands these three compounds CaO, P2O5 and SiO ₂ . This definition only makes it possible to quantify the respective proportions of the elements Ca, P and Si. These three elements can be present in the composition according to the invention in various forms such as Ca ₁₀ (PO ₄ ) ₆ OH ₂ , Ca ₃ (PO ₄ ) ₂ , Ca ₂ P ₂ O ₇ , SiO ₂ as described below.

The nature and the combination of the crystal structures present in the compositions according to the invention are important in order to then obtain the generation of hydroxyapatite.

Thus, this first mineral composition according to the invention has a combination of structures such that it has at least one crystallized part based on the structures: β Ca ₃ (PO ₄ ) ₂ , α Ca ₃ (PO ₄ ) ₂ , Ca ₂ P ₂ O ₇ and Ca ₁₀ (PO ₄ ) ₆ OH ₂ .

The presence of these four crystal structures: β Ca (PO ₄ ) ₂ , α Ca ₃ (PO ₄ ) ₂ , Ca ₂ P2θ ₇ and Ca ₁₀ (PO ₄ ) ₆ OH ₂ can be checked by RX structural analysis. It should however be noted that these different structures may have a shift in the line position on their RX spectra compared to the JCPDS data due to possible substitutions.

This type 1 composition may also comprise an amorphous part in addition to the crystallized part.

A global characterization of the amorphous part and the crystallized part is obtained by the nuclear magnetic resonance (NMR) technique. In general, the majority phases quantified by the ³¹ P NMR technique with acquisition of single pulse spectra and cross polarization are as follows: β Ca ₃ (PO ₄ ) ₂ , α Ca ₃ (PO ₄ ) ₂ and Ca ₁₀ (PO ₄ ) ₆ OH ₂ . The percentages of these majority phases can be determined by ³¹ P NMR by simulation of the experimental spectra from the spectra of the various basic compounds: β Ca ₃ (PO ₄ ) ₂ , α Ca ₃ (PO ₄ ) ₂ , Ca ₂ P2θ ₇ and Ca ₁₀ (PO ₄ ) ₆ OH ₂ .

For one of the preferred type 1 compositions, it is found by this method that the β Ca ₃ (PO ₄ ) ₂ phase is present in a content of at most 75% by weight relative to the composition, the α Ca ₃ phase ( PO ₄ ) ₂ is present in a content of between 10 and 30% by weight relative to the composition and Ca ₁₀ (PO ₄ ) ₆ OH ₂ is present in a content of between 10 and 45% by weight relative to the composition . The ³¹ P NMR spectra of this first composition according to the invention exhibit peaks characteristic of the various structures mentioned above.

- we find the following chemical shifts δ = +0.3 ppm, δ = +1, 5 ppm and δ = +4.8 ppm, which we attribute to β Ca ₃ (PO) ₂ ,

- we find the following chemical shifts δ = -0.3 ppm, δ = -0.1 ppm, δ = +0.6 ppm, δ = +0.9 ppm, δ = +1, 1 ppm, δ = + 1, 3 ppm, δ = +1, 8 ppm, δ = +2.4 ppm and δ = +4.1 ppm, which we attribute to α Ca ₃ (PO ₄ ) ₂ ,

- we find the following chemical shift δ = +2.8 ppm, which we attribute to Ca ₁₀ (PO ₄ ) ₆ OH ₂

This type 1 composition according to the invention must finally have a solubility such that, for 1 g of this composition dissolved in 5 g of water at a temperature of 90 ° C for 4 hours, the concentration of Ca ²⁺ is between 5 and 80 mg / l and the concentration of the different dissolved phosphate species, such as

3-

HPO, PO ₄ , expressed as P, is between 8 and 35 mg / l

The determination of Ca ²⁺ is carried out by ICP (plasma) and that of the phosphate species dissolved by colorimetry

The invention then relates to other mineral compositions, hydroxyapatite precursors, in particular of fibers, having an overall chemical composition, defined in the following system CaO-P ₂ θ5-Na ₂ O-Sιθ2, in molar proportions such as ratios (Ca Na P Si) = (1 xyz) satisfy the following conditions (b) 0 <x <0.6 0.6 <y <1, 0

0 <z <0.6

This overall chemical composition based on CaO-P ₂ θ5-Na ₂ O-Sιθ2 will be called quaternary as opposed to that seen previously in the CaO-P ₂ O ₅ -SιO _{2 system} called ternary Here also, it is the composition overall chemical, which does not mean that the precursor understands or only understands these four compounds CaO P2O5, Na ₂ O and Sι0, this definition only makes it possible to quantify the respective proportions of the elements Ca, Na, P and Si These four elements can be present in the composition according to the invention under various crystallized structures such as β Ca ₁₀ Na (PO ₄ ) ₇ , α Ca ₃ (PO ₄ ) ₂ NaCaPO ₄ , Ca ₂ P ₂ O ₇ , Na ₃ Ca ₆ (PO ₄ ) ₅ , SιO ₂ or in an amorphous form

Concerning these mineral compositions based on the quaternary system, an overall characterization of the amorphous part and of the crystallized part is obtained by NMR The ³¹ P NMR spectra obtained from these compositions present peaks characteristic of the various structures mentioned above.

- we find the following chemical shifts δ = -10.2 ppm, δ = -8.7 ppm, δ = -8 ppm, and δ = -7.1 ppm, which we attribute to Ca ₂ P2θ ₇ , - we find the following chemical shifts δ = - 3.8 ppm, δ = -1, 8 ppm, δ

= -0.4 ppm, δ = +3.7 ppm, δ = +5.6 ppm and δ = +7.0 ppm, which is attributed to Na ₃ Ca ₆ (PO ₄ ) ₅ , (the signals corresponding to this range of chemical shifts are wide signals),

- we find the following chemical shifts δ = +0.8 ppm, δ = +2.4 ppm, and δ = +3.5 ppm, which we attribute to β Ca ₁₀ Na (PO ₄ ) ₇

- we find the following chemical shift δ = +2.1 ppm, which we attribute to NaCaPO ₄

The presence of the crystalline phases can be checked by structural X-ray analysis and the presence of the phases comprising the crystalline and amorphous parts by ³¹ P NMR. These different structures can also present on their RX spectra a shift in the position of the lines in comparison with the JCPDS data. due to possible substitutions

The nature and the combination of the crystal structures present in the compositions based on this quaternary system are also important to then obtain the generation of hydroxyapatite.

Thus, there are two types of mineral compositions based on the quaternary system fulfilling the aims of the present invention. These compositions differ in the nature and the combination of their crystalline and amorphous phases.

In this quaternary system, the invention therefore relates to a second mineral composition, called type 2, having an overall chemical composition in molar proportions such that the ratios (Ca Na P Sι) = (1 xyz) verify the conditions (c) following 0 <x <0.4, 0.6 <y <1, 0,

0 <z <0.6, and a combination of structures such that it has at least one crystallized part based on the structures β Ca ₁₀ Na (PO ₄ ) ₇ NaCaPO ₄ and Ca ₂ P ₂ O ₇ and at least one part amorphous The presence of the two crystalline phases β Ca ₁₀ Na (PO) ₇ and NaCaPO ₄ can be checked by structural X-ray analysis and NMR analysis of phosphorus In general, these two phases are predominant, that is to say that they represent at least 50% by weight of the type 2 composition according to the invention In this quaternary system, the invention also relates to a third mineral composition, called type 3, having an overall chemical composition in molar proportions such that the ratios (Ca'Na P Si) = (1 x yz) verify the conditions ( d) following 0.4 <x <0.6, 0.6 <y <1, 0, 0 <z <0.6, and a combination of structures such that it has at least one crystallized part based on the structures β Ca ₁₀ Na (PO ₄ ) ₇ , NaCaP0 ₄ , Ca ₂ P ₂ O ₇ , Na ₃ Ca ₆ (PO ₄ ) ₅ and at least one amorphous part

The presence of these crystalline phases can be checked by structural X-ray analysis and NMR analysis of phosphorus. For a preferred type 3 composition, it is found by this method that the Na ₃ Ca ₆ (PO ₄ ) ₅ phase is present in a content of between 25 and 60% by weight relative to the composition, the β Ca ₁₀ Na (PO ₄ ) ₇ phase is present in a content of between 20 and 30% by weight relative to the composition, the NaCaPO ₄ phase is present in a content between 30 and 40% by weight relative to the composition and the Ca ₂ phase P2θ ₇ is present in a content between 1 and 6% by weight relative to the composition

For these two compositions of type 2 and 3 based on the quaternary system, the solubility must also be such that, for 1 g of this composition dissolved in 5 g of water at a temperature of 90 ° C. for 4 hours, the Ca ²⁺ concentration is between 0.5 and 50 mg / l and the concentration of the various dissolved phosphate species, expressed in P, is between 5 and 80 mg / l

In general, these mineral compositions according to the invention are in the form of powders These powders can be of variable particle size, in general, between 1 and 200 μm

Process for the preparation of mineral compositions

The invention also relates to a process for the preparation of mineral compositions, hydroxyapatite precursors as defined above. This process consists in implementing the following steps

1 - aqueous solutions and / or powders of compounds of Ca, Si, P and optionally Na, and optionally water, are mixed in amounts such as molar ratios (Ca Na'P Si) = (1 xyz) verify the conditions (a), (c) or (d) defined above,

2 - the mixture obtained is optionally dried, and

3 - this mixture is calcined at a temperature between 1000 and 1200 ° C for 2 to 48 hours

According to this process, the aqueous solutions, the powders and optionally the water are mixed in the proportions making it possible to obtain the molar ratios of the compositions according to the invention. Only aqueous solutions can be mixed, only powders and water, or mix both powders and aqueous solutions

The aqueous solutions or the powders can be chosen from the following compounds CaCO ₃ , CaO, Ca (OH) ₂ , Ca (NO ₃ ) ₂ , calcium salts such as, for example CaSO ₄ , 2H ₂ O, the compounds of phosphate such as, for example H ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ (H ₂ PO ₄ ), CaHPO ₄ , CaHP0 ₄ 2H ₂ O, Ca ₃ (PO ₄ ) ₂ , Na ₃ PO ₄ colloidal silicas, sodium silicates, Na ₂ CO ₃ , NaNO ₃ .

The mixing is carried out in the liquid phase, that is to say by mixing aqueous solutions or aqueous colloidal solutions or at least one of these solutions and powders, or even water. In general, the mixing is carried out with stirring.

This mixture can optionally be precipitated between steps 1 and 2 This precipitation can be carried out by any means known to those skilled in the art (pH control, for example addition of NH ₄ OH) Agitation can be maintained to homogenize the precipitate formed The mixture can then be allowed to dry to allow the water to evaporate, generally at room temperature, and the dried precipitate obtained is calcined

It is generally useful to control the basicity of the mixture during step 1 The value of this basicity must be adapted according to the starting materials used and the desired end products The value of this basicity can be determined by a person skilled in the art For example, if one proceeds with the addition of a solution of calcium salts, a solution of (NH ₄ ) ₂ HPO and a dispersion of colloidal silica of alkaline pH, the basicity of the medium can be adjusted by adding an ammonia solution to the (NH ₄ ) ₂ HPO _{4 solution} , the amount of ammonia added preferably corresponding to an OH / P0 ₄ molar ratio of between 0.5 and 1, even more preferably between 0.7 and 1, so as to obtain the Na ₃ Ca ₆ (PO) ₅ phase after calcmation

The optionally dried product is then calcined. It can be calcined, in air or in a controlled atmosphere. Preferably, the calcmation time is between 6 and 48 hours. In an optimized mode, the calcmation is carried out by raising temperature at a speed of between 50 and 500 ° C / hour, preferably between 100 and 400 ° C / hour, even more preferably of the order of 300 ° C / hour, up to a temperature of between 1000 ° C and 1200 ° C, then maintained at this temperature for 6 to 48 hours The temperature of calcmation can be optimized according to the conditions of the stage of precipitation (nature of the salts, pH of the aqueous solutions raw materials) One can, for example, privilege the formation of the compound Na ₃ Ca ₆ (P0 ₄ ) ₅ by calcining at 1000 ° C. This optimization is within the reach of those skilled in the art

After calcmation, the solid obtained is optionally ground, the grinding size can vary between 1 and 200 μm. It is also possible to carry out successive alternating calcmations of grinding operations, in particular if it is desired to mix the powder of the mineral composition according to l invention with a mineral binder

Use of mineral compositions for the preparation of hydroxyapatite.

The invention also relates to the use of the mineral compositions described above for the preparation of hydroxyapatite and in particular of hydroxyapatite fibers.

The invention thus relates to the process for the preparation of hydroxyapatite, in particular in the form of fibers, from the mineral compositions described above, in which at least one of said mineral compositions is hydrated. In fact, the mineral compositions defined above, put in certain hydration conditions, develop the hydroxyapatite structure It is assumed that during hydration, phenomena of dissolution / repepitation of the mineral compositions take place at kinetics such that they lead to the formation of the majority hydroxyapatite crystalline phase especially in the form of fibers

A particular characteristic of this process for the preparation of hydroxyapatite lies in the fact that hydration can be carried out in the presence of a particularly small amount of water. Thus, hydration can be carried out for a weight ratio of water / mineral composition. at most 1.5, preferably at most 0.6

Another particular characteristic of this preparation process lies in the fact that the hydration can be carried out at a pH between 10 and 13, preferably at a pH between 10 and 12.5 Hydroxyapatite, in particular hydroxyapatite fibers, can be obtained, for example, in the presence of ammonia, lime or soda

In general, hydration is carried out at a temperature of at least 60 ° C, preferably at most 120 ° C If the temperature is above 100 ° C, the process proceeds hydration is implemented, for example, in an autoclave or in a closed enclosure with controlled humidity or not (Parr bomb, for example) If the temperature is lower than 100 ° C, one can use a saturated gas flow of water vapor at hydration temperature The hydration time can vary between 4 hours and 120 hours

In this context, the invention also relates to fibers of hydroxyapat ⁱ te obtained from the previously defined preparation process and having a length of at least 2 μm and a diameter of at least 0.1 μm. The apatite structure of these fibers may or may not be substituted, for example, by

Na +, silicates, carbonates or acid phosphates, which produce non-stoichiometric apatite structures

The invention also relates to the use of the fibers obtained by hydration of the preceding mineral compositions for reinforcing the biomaterials

The invention also relates to the use in plastics of fibers obtained by hydration of the above mineral compositions

Use of mineral compositions in concrete

The invention relates more particularly to the use for reinforcing concrete of at least one of the following compositions, a type 1 composition for which 0.5 <y <0.65 and 0.2 <z <0.6,

^> a composition of type 3 for which 0.4 <x <0.6, 0.6 <y <1 and 0 <z <0.6, and preferably 0.45 <x <0.55, 0, 8 <y <0.9 and 0.2 <z <0.4, or

^ a mineral composition having a chemical composition defined in the following system CaO-P ₂ O ₅ , in molar proportions such that the ratio (Ca P) = (1 y) satisfies the following condition 0.62 <y <0.75

As such, the invention relates to a process for the preparation of concrete reinforced with hydroxyapatite in which at least one hydraulic binder is mixed, water from the aggregates and at least one of the following compositions, a type 1 composition for which 0.5 <y <0.65 and 0.2 <z <0.6, ^ a type 3 composition for which 0.4 <x <0.6, 0.6 <y <1 and 0 <z < 0.6 and preferably 0.45 <x <0.55, 0.8 <y <0.9 and 0.2 <z <0.4, or

^ a mineral composition having a chemical composition defined in the following system CaO-P ₂ O ₅ , in molar proportions such that the ratio (Ca P) = (1 y) satisfies the following condition 0.62 <y <0.75 According to a first variant of this process, at least one hydraulic binder, water, aggregates and at least one of the following compositions are mixed

• => a type 1 composition for which 0.5 <y <0.65 and 0.2 <z <0.6, or ^> a mineral composition having a chemical composition defined in the system following CaO-P ₂ O ₅ , in the molar proportions such that the ratios (Ca P) = (1 y) verify the following condition 0.64 <y <0.68, then this mixture is heated between 50 and 120 ° C, preferably between 60 and 100 ° C, for a period of between 6 hours and 4 weeks, preferably between 6 and 48 hours

According to this first variant, a concrete is generally obtained comprising crystallized hydroxyapatite. If the mixture is heated to more than 60 ° C., hydroxyapatite fibers can be obtained.

According to a second variant of this process, at least one hydraulic binder, water, aggregates and at least one mineral composition chosen from the type 3 compositions for which 0.4 <x <0.6, 0, are mixed, 6 <y <1 and 0 <z <0.6, and preferably 0.45 <x <0.55, 0.8 <y <0.9 and 0.2 <z <0.4, then this mixture is heated between 100 and 150 ° C, preferably between 100 and 120 ° C, for a period of between 6 hours and 4 weeks, preferably between 6 and 48 hours

According to this second variant, a concrete is generally obtained comprising hydroxyapatite crystallized in the form of fibers.

According to this process for preparing reinforced concrete, the ratio by weight of mineral composition to the hydraulic binder + the mineral composition is generally between 0.2 and 0.65, preferably between 0.25 and 0.5

For the two variants, the ratio t by weight of water to the mineral composition + the binder is generally between 0.25 and 1.5 and preferably between 0.25 and 0.5, and the ratio s by weight water / binder is generally between 0.25 and 0.5

With regard to mixing, it is possible to mix the hydraulic binder and the aggregates on the one hand, and mix the mineral composition and the water on the other hand, then mix the two mixtures obtained. It is also possible to mix the hydraulic binder the aggregates. and at least one mineral composition, then add water to this mixture

The binder can be, for example, of the calcium silicate (Ca ₃ SιO ₅ ) or Portland type from Lafarge A binder can be used comprising at least one mineral composition, said mineral composition having been incorporated into the binder during its manufacture

It is possible to add to the mixture of hydraulic binder, water, aggregates and the mineral composition, the additives conventionally used in mortar formulations such as

- silica smoke in a hydraulic binder / silica weight ratio of at most 0.35,

- fluidizers such as lignosulfonates, casein, formaldehyde derivatives, alkali metal polyacrylates, alkali metal polycarboxylates, grafted polyethylene oxides, polynaphthalene sulfonates, polymelamine sulfonates in a weight ratio of hydraulic binder / fluidifier not more than 0.03 pure

Finally, the invention relates to a concrete capable of being obtained by the above process, the concrete comprising crystallized hydroxyapatite

In this concrete, the crystallized hydroxyapatite can be at least partially in the form of fibers. These fibers can have a length of at least 2 μm and a diameter of at least 0.1 μm.

The following examples illustrate the invention without however limiting its scope

EXAMPLES

Example 1: Type 3 mineral composition

A solution A is prepared by diluting 150 ml of sodium silicate (2M in Sι0 ₂ and of molar ratio Rm (SιO ₂ / Na ₂ O) = 1), with distilled water to a volume of 200 ml

Was dissolved 132 g of (NH _{4) 2} HP0 in ^water, then added 95 ml of 20% ammonia and water is added to a final volume of 450 ml was obtained a solution B

Solution C is prepared by dissolving 196.8 g of Ca (NO ₃ ) ₂ in 450 ml of distilled water

Solution A is introduced into a beaker with a capacity of 2 liters and then placed under stirring at 450 rpm. Solutions B and C are added simultaneously and quickly. A white gel is observed. As soon as the mixture begins to solidify, the stirring speed is increased to 1500 rpm to homogenize

I together Then, the stirring speed is gradually slowed down to 800 rpm and the mixture is still allowed to stir for 15 m. A product of composition (Ca Na P Si) is obtained _m0 ι _e = (1 0.5 0.833 0.25) It is placed in a cnstallisor It is left to dry at room temperature 2 days, then drying ends at 120 ° C. overnight The solid obtained is calcined according to the following temperature profile, raised to

300 ° C / h up to 1040 ° C, step of 6 h at 1040 ° C and lowering to free temperature The product is finally ground

By particle size analysis, an average diameter of approximately 100 μm is determined. By X-ray diffraction, the lines characteristic of the following structures are mainly observed Na ₃ Ca ₆ (PO ₄ ) ₅ (main line), NaCaPO ₄ , β NaCa ₀ ( PO) ₇ By ³¹ P NMR, the following lines are confirmed

- δ = -3.8 ppm, δ = -1.8 ppm, δ = -0.4 ppm, δ = +3.7 ppm, δ = +5.6 ppm and δ = +7.0 ppm, which are broad lines attributable to Na ₃ Ca ₆ (PO ₄ ) ₅ - δ = +2.1 ppm attnbutable to NaCaPO ₄

- δ = +0.8 ppm, δ = +2.4 ppm and δ = +3.5 ppm, which are attributable to β NaCa ₁₀ (PO ₄ ) ₇

- δ = -10.2 ppm, δ = -8.7 ppm, δ = -8 ppm, and δ = -7.1 ppm, which we attribute to Ca ₂ P ₂ O ₇

Example 2: Use of the mineral composition of Example 1 as a precursor of hydroxyapatite fibers in a C ₃ S matrix.

5 g of the mineral composition of Example 1 are added to 10 g of hydraulic binder C ₃ S (binder obtained by temperature regulation of powders of SιO ₂ and CaCO ₃ , with a specific surface <1 m ² / g) After mixing the powders by kneading with a spatula for about 3 mm, 21 g of deionized water are added, corresponding to a weight ratio of water / (luant + mineral composition) of 1, 4 The mixture is kneaded for 3 min until obtaining a paste The paste is left for approximately 15 mm at room temperature, then it is introduced into a teflon shirt autoclave with a diameter of approximately 45 mm and a height of 90 mm (Parr bomb). The autoclave is then introduced into an oven carried to 120 ° C The temperature is maintained for 16 hours, then cooled to room temperature

The object obtained is then fractured On a fracture facies, observation with a scanning electron microscope highlights the presence of fibers with a length of approximately 2 μm and a diameter of approximately 0.2 μm A fragment of the object obtained is ground. The powder resulting from the grinding is analyzed by X-ray diffraction. The following phases are observed.

- The phases initially present in the clmker or in the mineral composition of Example 1, namely Ca ₃ SιO ₅ and NaCaPO ₄

- Phases generated by the hydration of cl ker or the mineral composition of Example 1 Ca ₁₀ (PO4) ₆ (OH) ₂ , Ca ₆ (Sι ₂ O ₇ ) (OH) ₆ , Ca (OH) ₂

Fragments of the object are ground in a mortar and the powder obtained is dry dispersed on a carbon membrane with holes to avoid any chemical modification of the sample. By transmission electron microscopy (MET Philipps CM 30 microscope), cπstaux are observed. with fibrous morphology The point chemical analysis, coupled with transmission electron microscopy, carried out on these fibers, shows the presence of phosphorus and calcium

Example 3: Use of the mineral composition of Example 1 as a precursor of hydroxyapatite fibers in a Portiand matrix.

The conditions of example 2 are repeated, except that Portiand cement from the company Lafarge is used in place of the binder C ₃ S. Portiand cement is obtained by calcination of CaCO ₃ and Sι0 ₂ powders , it is characterized by the presence of the following phases C ₃ S, C ₂ S, C ₃ A, C ₄ AF visualized by X-ray diffraction The surface Blame is about 3000

As in Example 2, we observe by X-ray diffraction, the presence of the hydroxyapatite phase, Ca-ιo (P l'h4) ₆ (OH), generated by the hydration of the mineral composition

On a fracture facies, observation with a scanning electron microscope highlights the presence of fibers with a length of around 2 μm and a diameter of around 0.2 μm

Example 4: type 1 mineral composition

Solution A is prepared by dissolving 170.5 g of Ca (N0 ₃ ) ₂ in 400 ml of deionized water

83.2 g of (NH ₄ ) ₂ HPO are dissolved in 250 ml of water, then 270 ml of 2M ammonia are added. Solution B is obtained. A solution C is prepared by diluting 60 ml of Ludox AS 40 (colloidal dispersion of silica at 40% by weight of SιO ₂ sold by Du Pont) in a final volume of 200 ml of permuted water

Pour solution C into a 2-liter beaker and keep stirring mechanically at 300 rpm. Instantly pour solution B, then solution A The mixture solidifies. The stirring speed is gradually increased until at 1500 rpm to homogenize. A gel is obtained which becomes more fluid after about 30 seconds. Stirring is continued for 5 mm at 800 rpm. The mixture is then poured into a large installer and allowed to dry at room temperature for 2 days Drying is ended by keeping it at 120 ° C overnight in an oven

The composition of the mixture is as follows (Ca P Si) _m0 | _e = (1 0.6 0.5)

The product is calcined according to the following temperature profile ascent at 300 ° C / h up to 1050 ° C, leveling from 6 h at 1050 ° C and free descent in temperature

The product is then ground. Its particle size is approximately 80 μm

By X-ray diffraction, the majority phase β Ca ₃ (PO) ₂ and the α phases Ca ₃ (PO ₄ ) ₂ and Ca ₁₀ (PO4) ₆ (OH) ₂ are observed.

By ³¹ P NMR, we observe different lines attributable to these following compounds

- δ = +0.3 ppm, δ = +1, 5 ppm and δ = +4.8 ppm attributable to β Ca ₃ (PO ₄ ) ₂

- δ = -0 3 ppm, δ = -0.1 ppm, δ = +0.6 ppm, δ = +0.9 ppm, δ = +1, 1 ppm, δ = +1, 3 ppm, à = +1.8 ppm, δ = +2.4 ppm, δ = +4.1 ppm attributable to α Ca ₃ (P0 ₄ ) ₂

- b = +2.8 ppm attributable to Ca ₁₀ (PO4) ₆ (OH) ₂ An increase in the ratio r [r = intensity of the peak corresponding to a is observed

Ca ₁₀ (PO4) ₆ (OH) ₂ / (intensity of the peak corresponding to α Ca ₃ (PO ₄ ) ₂ + intensity of the peak corresponding to βCa ₃ (PO ₄ ) ₂ )] after hydration in the autoclave, indicating the transformation of the mineral composition into hydroxyapatite In addition, this transformation into hydroxyapatite is confirmed by ³ P NMR

Example 5: Use of the mineral composition of Example 4 as a hydroxyapatite precursor in the Portiand matrix.

5 g of the mineral composition of Example 4 are added to 10 g of the Portiand binder as described in Example 3 After mixing the powders by kneading with a spatula for approximately 3 min, 4 g of deionized water corresponding to a water / cement weight ratio of 0.4 The mixture is kneaded for 3 min until a paste is obtained After a stay of about 15 mm at room temperature, the paste is introduced into a teflon-coated autoclave with a diameter of about 45 mm and a height of 90 mm.

(Parr spray) Then, the autoclave is introduced into an oven brought to 90 ° C. The temperature is maintained for 3 weeks Then, the autoclave is cooled to room temperature

A fragment of the object obtained is ground. The powder resulting from the grinding is analyzed by X-ray diffraction. The following phases are observed.

the phases initially present in the clmker or in the mineral composition of Example 4, namely Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , Ca ₃ Sι0 ₅ , α Ca ₃ (PO ₄ ) ₂ and β Ca ₃ (PO ₄ ) ₂ , - phases generated by the hydration of the clmker or of the mineral composition of Example 4 Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ and Ca (OH) ₂

There is an increase in the ratio r [r = intensity of the peak

Caι ₀ (PO ₄ ) ₆ (OH) ₂ / (intensity of the peak corresponding to αCa ₃ (PO) ₂ + intensity of the peak corresponding to βCa ₃ (PO) ₂ )] after hydration in the autoclave, indicating the transformation of the mineral composition into hydroxyapatite In addition, this transformation of the mineral composition into hydroxyapatite is confirmed by P NMR

This example illustrates the in situ formation of crystallized hydroxyapatite

Example 6: Use of the mineral composition of Example 4 as a hydroxyapatite precursor in a Portiand matrix and in the presence of Si0 ₂ .

2 g of silica smoke and 5 g of mineral composition obtained according to the method of Example 4 (except that the temperature has set at 1100 ° C.) are added to 10 g of the Portiand binder as described in example 3

After mixing the powders by kneading with a spatula for about 3 min, 4 g of deionized water is added corresponding to a water / cement ratio by weight of 0.4 The mixture is kneaded for 3 mm until a paste is obtained. stay of about 15 mm at room temperature, the paste is introduced into a teflon shirt autoclave with a diameter of about 45 mm and a height of 90 mm (Parr bomb) The autoclave is introduced into an oven brought to 90 ° C. The temperature for 3 weeks then cooled to room temperature

A fragment of the object obtained is ground. The powder resulting from the grinding is analyzed by X-ray diffraction. The following phases are observed.

the phases initially present in the clmker or in the starting mineral composition, namely Ca ₃ SιO ₅ and α and β Ca ₃ (PO ₄ ) ₂ , - phases generated by the hydration of the clmker or the starting mineral composition. Ca ₁₀ (PO4) ₆ (OH) ₂ and Ca (OH) ₂

Thus, this example illustrates the m situ formation of crystallized hydroxyapatite

Example 7: mineral composition in the CaO-P ₂ 0 _{5 system}

A solution A is prepared by dissolving 166.3 g of Ca (NO ₃ ) ₂ in a final volume of 400 ml of deionized water. 89.2 g of (NH ₄ ) ₂ HPO _{4 are} dissolved in 250 ml of water, then add 270 ml of 2 M ammonia solution B is obtained

Solution B is poured into a 2 liter beaker and kept under mechanical stirring at 300 rpm. Solution A is poured instantly into solution B The mixture solidifies. The stirring speed is gradually increased up to 1500 rpm to homogenize. Stirring is continued for 5 mm at 800 rpm The mixture is then poured into a large cnstaller and allowed to dry at room temperature for 2 days. The drying is terminated by keeping it at 120 ° C. overnight in an oven. The composition of the mixture is (Ca -P) _m0 | _Θ = (10.66)

The product is calcined according to the following temperature profile rising to 300 ° C / h up to 1100 ° C, leveling from 6 h to 1100 ° C and free drop in temperature The product is then ground Its particle size is approximately 80 μm

By X-ray diffraction, the majority phase β Ca ₃ (PO ₄ ) ₂ and the crystallized minority phases α Ca ₃ (PO) ₂ and Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ are observed.

Example 8: Use of the mineral composition of Example 7 as a hydroxyapatite precursor in a Portiand matrix

5 g of the mineral composition of Example 7 are added to 10 g of Portiand binder as defined in Example 3 After mixing the powders by kneading with a spatula for approximately 3 min, 4 g of corresponding permuted water are added at a water / cement weight ratio of 0.4 The mixture is kneaded for 3 min until a paste is obtained

After a stay of about 15 mm at room temperature, the paste is introduced into a teflon-coated autoclave with a diameter of about 45 mm and a height of 90 mm (Parr bomb). The autoclave is introduced into an oven brought to 90 ° C. On maintains the temperature for 4 weeks, then cools to room temperature A fragment of the object obtained is ground. The powder resulting from the grinding is analyzed by X-ray diffraction. The presence of the following phases is observed:

- the phases initially present in the clinker or in the mineral composition of Example 7, namely: Ca ₃ SiO ₅ and α and β Ca ₃ (PO) ₂ , - phases generated by the hydration of the clinker or of the mineral composition of Example 7: Ca ₁₀ (PO4) ₆ (OH) ₂ and Ca (OH) ₂ .

An increase in the ratio r [r = intensity of the peak corresponding to

Ca ₁₀ (PO4) ₆ (OH) ₂ / (intensity of the peak corresponding to α Ca ₃ (PO ₄ ) ₂ + intensity of the peak corresponding to βCa ₃ (PO ₄ ) ₂ )] after hydration in the autoclave, indicating the transformation of the mineral hydroxyapatite composition. In addition, this transformation into hydroxyapatite is confirmed by ³¹ P NMR.

Fragments of the object are ground in a mortar and the powder obtained is dry dispersed on a carbon membrane with holes to avoid any chemical modification of the sample. By transmission electron microscopy (MET Philipps CM 30 microscope), crystals with fibrous morphology are observed. The point chemical analysis, coupled with transmission electron microscopy, performed on these fibers, shows the presence of phosphorus and calcium.

Claims

1 Mineral composition, precursor of hydroxyapatite fibers, characterized in that it has - a chemical composition defined in the following system CaO-P ₂ O ₅ -Sιθ2, in molar proportions such as the ratios (Ca P Si) = (1 yz) satisfy the following conditions (a) 0.5 <y <0.8 0.2 <z <0.6 - a combination of phases such that it has at least one crystallized part based on the β Ca phases ₃ (PO ₄ ), α Ca ₃ (PO ₄ ) ₂ , Ca ₂ P ₂ O ₇ and Ca ₁₀ (PO ₄ ) ₆ OH ₂ ,

a solubility such that for 1 g of this composition dissolved in 5 g of water at a temperature of 90 ° C for 4 hours, the concentration of element Ca ²⁺ is between 5 and 80 mg / l and the concentration of the different dissolved phosphate species, expressed as P, is between 8 and 35 mg / l

2 mineral composition according to claim 1, characterized in that

- the β Ca ₃ (PO ₄ ) ₂ phase is present in a content of at most 75% by weight relative to the composition, - the α Ca ₃ (PO ₄ ) ₂ phase is present in a content of between 10 and 30% by weight relative to the composition and

- the Caι ₀ (PO ₄ ) ₆ OH ₂ phase is present in a content of between 10 and 45% by weight relative to the composition

3 Mineral composition, precursor of hydroxyapatite fibers, characterized in that it has

- a chemical composition defined in the following system CaO-P ₂ θ5-Na ₂ O-Sιθ2, in molar proportions such that the ratios (Ca Na P Si) = (1 xyz) satisfy the following conditions (c) 0 <x <0.4 0.6 <y <1 0 <z <0.6

- a combination of phases such that it has at least one crystallized part based on the phases β Ca ₁₀ Na (PO ₄ ) ₇ NaCaPO ₄ and Ca ₂ P ₂ O ₇ , β Ca ₁₀ Na (PO ₄ ) ₇ and NaCaPO ₄ , these last two phases representing at least 50% of the composition,

a solubility such that for 1 g of this composition dissolved in 5 g of water at a temperature of 90 ° C for 4 hours, the concentration of Ca ²⁺ is included between 0.5 and 50 mg / l and the concentration of the various dissolved phosphate species, expressed in P, is between 5 and 80 mg / l.

4 Mineral composition, precursor of hydroxyapatite fibers, characterized in that it has

- a chemical composition defined in the following system CaO-P ₂ O ₅ -Na2θ-Sιθ2, in molar proportions such that the ratios (Ca Na P Si) = (1: xy: z) verify the following conditions (d)

0.4 <x <0.6 0.6 <y <1 0 <z <0.6

a combination of phases such that it has at least one crystallized part based on the β Ca ₁₀ Na (PO ₄ ) ₇ , NaCaPO ₄ , Ca ₂ P ₂ O ₇ and Na ₃ Ca ₆ (PO ₄ ) ₅ phases,

a solubility such that for 1 g of this composition dissolved in 5 g of water at a temperature of 90 ° C for 4 hours, the Ca ²⁺ concentration is between 0.5 and 50 mg / l and the concentration of the various dissolved phosphate species, expressed in P, is between 5 and 80 mg / l.

5 mineral composition according to claim 4, characterized in that - the Na ₃ Ca ₆ (PO ₄ ) ₅ phase is present in a content of between 25 and 60% by weight relative to the composition,

the β Ca ₁₀ Na (PO ₄ ) ₇ phase is present in a content of between 20 and 30% by weight relative to the composition,

the NaCaP0 ₄ phase is present in a content of between 30 and 40% by weight relative to the composition,

- the Ca ₂ P2θ ₇ phase is present in a content of between 1 and 6% by weight relative to the composition

6 Mineral composition, precursor of hydroxyapatite fibers, according to one of claims 1 to 3, characterized in that it is in powder form

7 Process for preparing a mineral composition according to one of claims 1 to 5, characterized in that the following steps are implemented

1 - mixing aqueous solutions and / or powders of compounds of Ca, Si P and optionally Na, and optionally water in amounts such that the molar ratios (Ca Na P Si) = (1 xyz) verify the conditions (a), (c) or (d) defined above,

2 - the mixture obtained is optionally dried, and 3 - this mixture is calcined at a temperature between 1000 and 1200 ° C for 2 to 48 hours.

8 preparation process according to claim 7, characterized in that the mixture is precipitated between steps 1 and 2

9 Preparation process according to claim 7 or 8, characterized in that the calcined products obtained are ground

10 Preparation process according to one of claims 7 to 9, characterized in that one proceeds to the addition of a solution of calcium salts, a solution of (NH) ₂ HPO and a dispersion of silica colloidal of alkaline pH, the basicity of the medium being adjusted by adding an ammonia solution to the solution of (NH ₄ ) ₂ HPO ₄ , the amount of ammonia added corresponding to an OH / PO molar ratio of between 0, 5 and 1.

11 Preparation process according to any one of claims 7 to 10, characterized in that the aqueous solutions or the powders can be chosen from

CaCO ₃ , CaO, Ca (OH) ₂ , Ca (NO ₃ ) ₂ , calcium salts such as, for example CaSO ₄ , 2H ₂ O, phosphate compounds such as, for example H ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ (H ₂ PO ₄ ), CaHPO ₄ , CaHP0 ₄ 2H ₂ 0, Ca ₃ (PO ₄ ) ₂ , Na ₃ PO ₄ colloidal silicas, sodium silicates, Na ₂ CO ₃ , NaNO ₃

12 Proceeds according to any one of claims 7 to 11, characterized in that, the calcmation is carried out by temperature rise at a speed between 50 and

500 ° C / hour up to a temperature between 1000 ° C and 1200 ° C, then maintaining at this temperature for 6 to 48 hours

13 Use of the mineral compositions according to one of claims 1 to 6 for the preparation of hydroxyapatite

14 Use according to the preceding claim for the preparation of hydroxyapatite fibers

15 Process for the preparation of hydroxyapatite, characterized in that at least one mineral composition according to one of claims 1 to 6 is hydrated

16. Method according to the preceding claim, characterized in that the hydration is carried out for a weight ratio of water / mineral composition of at most 1.5.

17. The method of claim 15 or 16, characterized in that the hydration is carried out at pH between 10 and 13.

18. Method according to any one of claims 15 to 17, characterized in that during the hydration the temperature is at least 60 ° C.

19. Method according to any one of claims 15 to 18, characterized in that the hydration time is between 4 hours and 120 hours.

20. Hydroxyapatite fibers from the preparation process according to one of claims 15 to 19, characterized in that they have a length of at least 2 μm and a diameter of at least 0.1 μm.

21. Use of hydroxyapatite fibers according to claim 20 for the reinforcement of plastic materials.

22. Use of hydroxyapatite fibers according to claim 20 for the reinforcement of biocompatible materials.

23. Use for reinforcing concrete of at least one of the following compositions

- a composition according to claim 1 or 2 for which 0.5 <y <0.65 and 0.2 <z <0.6,

- A composition according to claim 4 or 5 for which 0.4 <x <0.6, 0.6 <y <1 and 0 <z <0.6, or

a mineral composition having a chemical composition defined in the following system: CaO-P ₂ O, in molar proportions such as the ratios:

(Ca: P) = (1: y) satisfy the following condition: 0.62 <y <0.75.

24. Process for preparing concrete reinforced with hydroxyapatite in which at least one hydraulic binder, water, aggregates and at least one of the following compositions are mixed:

- a composition according to claim 1 or 2 for which 0.5 <y <0.65 and 0.2 <z <0.6, - A composition according to claim 4 or 5 for which 0.4 <x <0.6, 0.6 <y <1 and 0 <z <0.6, or

- a mineral composition having a chemical composition defined in the following system. CaO-P ₂ O ₅ , in molar proportions such that the ratios (Ca P) = (1: y) satisfy the following condition 0.62 <y <0.75.

25 Method according to the preceding claim, characterized in that

- Mixing at least one hydraulic binder, water, aggregates and at least one of the following compositions. a composition according to claim 1 or 2 for which 0.5 <y <0.65 and 0.2 <z

<0.6, or a mineral composition with a chemical composition defined in the following system. CaO-P ₂ O ₅ , in molar proportions such as ratios

(Ca: P) = (1: y) verify the following condition: 0.64 <y <0.68, - then this mixture is heated between 50 and 120 ° C for a period of between 6 hours and 4 weeks.

26 Method according to the preceding claim, characterized in that the mixture is heated to more than 60 ° C.

27 Method according to claim 24, characterized in that

- Mixing at least one hydraulic binder, water, aggregates and at least one mineral composition chosen from the compositions according to claim 4 or 5 for which 0.4 <x <0.6, 0.6 <y < 1 and 0 <z <0.6, and preferably 0.45 <x <0.55, 0.8 <y <0.9 and 0.2 <z <0.4,

- then this mixture is heated between 100 and 150 ° C for a period of between 6 hours and 4 weeks

28 Method according to one of claims 24 to 27, characterized in that the weight ratio of mineral composition on the hydraulic binder + the mineral composition is between 0.2 and 0.65

29 Method according to one of claims 24 to 28, characterized in that the weight ratio s water / hydraulic binder is between 0.25 and 0.5

30 Method according to one of claims 24 to 29, characterized in that the weight ratio t of water on the mineral composition + the binder is between 0.25 and 1.5

31. Method according to one of claims 24 to 30, characterized in that the hydraulic binder and the aggregates are mixed, then a mixture of at least one mineral composition and water is added thereto.

32. Method according to one of claims 24 to 30, characterized in that the hydraulic binder, the aggregates and at least one mineral composition are mixed, then water is added to this mixture.

33. Method according to one of claims 24 to 28, characterized in that a binder is used comprising at least one mineral composition, said mineral composition having been incorporated into the binder during its manufacture.

34. Concrete capable of being obtained by the process according to one of claims 24 to 33, characterized in that it comprises crystallized hydroxyapatite.

35. Concrete according to the preceding claim, characterized in that the crystallized hydroxyapatite is at least partially in the form of fibers with a length of at least 2 μm and a diameter of at least 0.1 μm.